Process of obtaining metallic aluminium or other metals by electrolysis.



Patented Dec. 9, I902.

G. TADDEI. PROCESS OF OBTAININGMEIALLIC ALUMINIUM OR OTHER METALSBYELECT'BDLYSIS.

(Application filed July 17, 1901.)

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Patented Deb. 9, I902.

G. TADDEI. PROCESS OF OBTAININGMETALLIG ALUMINIUM OR OTHER METALS BYELEGTROLYSIS.

(Application filed July 17, 1901.)

3 Sheets-Sheet a.

(No'ModeL) UNITED STATES PATENT OFFICE.

GIROLAMO TADDEI, OF TURIN, ITALY, ASSIGNOR TO THE SOGIETA ITALlANA DIAPPLIOAZI ONI ELETTRIOHE, OF TURIN, ITALY.

, PROCESS OF OBTAINING METALLIC ALUMINIUM OR OTHER METALS'BYELECTROLYSIS.

SPECI EFIGA TION forming part of Letters Patent No. 715,625, datedDecember 9, 1902..

7 Application filed J'uly 1'7, 190].- Serial No. 68,575. (No specimens.)

To all whom it may concern:

Be it known that I, GIROLAMO TADDEI, a subject of the King of Italy,residingin Turin, Italy, haveinvented a certain new and useful Method ofObtainingMetals from Their Compounds, of which the following is aspecification.

This invention relates to a process for obtaining metals from theircompounds, and particularly the metal aluminium from its oxid; and theobject of the invention is to effect this recovery of the metal with theminimum of energy thermoelectrically considered in relation toindustrial conditions and to effect it in an automatic or substantiallyautomatic and continuous sequence of steps or operations.

The process will be readily understood from a description of theoperations required for reducing alumina (A1 0 to recover the metalaluminium therefrom. The alumina suitably dehydrated is mixed with tarto form balls or masses in which the carbon and aluminium are insubstantially equivalent proportions viz., six of carbon to 9.1 ofaluminium.

The operations or steps of the process are as follows:

1. Fused sodium chlorid (NaCl) is decomposed by electrolysis and itselements in the form of vapor separated. The heat employed will be about1,000 centigrade, and the current employed will be continuous and have atension of about 4.5 volts.

2. The chlorin from the step or operation 1 is led to a closed vesselcontaining the mass of alumina and tar above described. This vessel andits contents are heated up to from 1,300 to 1,500 centigrade, and thechlorin is gradually brought into contact with all parts of the masstherein, thus producing a reaction, from which results aluminium chloridand carbonic oxid, as expressed in the following:

3. The aluminium chlorid from the reaction of the step 2 will be in theform of vapor, and it passes 0%, together with the carbonic oxid, toanother vessel, where it mingles with the hot sodium vapor from thestep 1. This intermingling of the hot vapors produces another reaction,the sodium combining with the chlorin of the aluminium chlorid andsetting free the carbonic oxid and the metal aluminium. The reaction isexpressed in the following:

Thus the metal aluminium is separated, the sodium chlorid is recoveredwithout loss for use again, and the carbonic oxid passes ofli and may beburned. The operations are contin none, the mixture of alumina and tarproducing continuously aluminium and carbonic oxid. The sodium andchlorin separately and in combination move in a closed circuit withoutwaste or being consumed.

In order to make the practical and industrial carrying out of my processthe better understood, reference may be had-to the accompanyingdrawings, which illustrate an apparatus that may be employed in theprocess.

In the drawings, Figure l is a general plan of the apparatus, and Fig. 2isa longitudinal vertical section of the same in the plane indicatedbyline 00 in Fig. 1. Fig. 3 is a vertical transverse section at line 00in Fig. 1. Fig. 4 is a horizontal section at line 00 in Fig.3.

Fig. 5 is a vertical transverse section at line i 00 in Fig. 1. Fig. 6is a horizontal section at line 00 in Fig: 5. Fig. 7 is a verticaltransverse section at line m in Fig. 1, and Fig. 8 is a horizontalsection at line :0 in Fig. 7.

The construction of the apparatus will be readily understood from thedrawings and the following description:

For convenience of description the apparatus may be considered asdivided into three sectionsnamely, the elect-rolyzing-section E, thechlorinating-section G, and the substituting-section S. The severalsections of the apparatus will be described in the order given above.

The operative features of the apparatus are set in brickwork or masonryM. The first or electrolyzing section E consists of a vessel 1,

into which depend separator-tubes 2, fixed at their upper ends in aninner cover 3. The carbon anodes4 depend in these tubes 2 from an upperor outer cover 5, elevated above the cover 3. The downwardly-flangedmargins of the covers rest in a trough 6 about the vessel 1. At the sideof the vessel 1 and connecting therewith by apertures 7 below the levelof the electrolyte 8 is a vessel 9 for introducing the electrolyte oradding thereto during the process.

10 represents the iron cathodes, situated between the carbon anodes.

11 is a pipe for drawing ofi the metallic aluminium, as will behereinafter explained.

12 is a heater in a chamber beneath the vessel 1 for burning carbonicoxid (CO) mixed with heated air, as will be explained.

From the space between the two covers 3 and 5 two pipes 13 lead to thesecond or chlorinating section of the apparatus, and a pipe 14 leadsfrom the interior of the vessel 1 to the section S.

The second section of the apparatus (seen in detail in Figs. 5 and 6)consists of a vessel 15, set in the brickwork over the heater 16. Thisvessel is divided transversely by a partition into two chambers, eachprovided with a cover 17. Each chamber has a perforated bottom 18,situated some distance above the imperforate bottom, and the pipes 13enter the space between these bottoms. A hopper 19 supplies material tothe two chambers in the -vessel 15, and pipes 20 lead from the upperparts of the respective chambers in the vessel to the section S.

The third section S of the apparatus (seen in detail in Figs. 7 and 8)comprises a vessel 21, set in the brickwork and divided transversely bya partition 22 into two chambers provided with covers 23. There is alsoin each chamber a horizontal partition 24, which extends from thepartition 22 part way across the chamber. The pipes from the vessel 15and the pipe 14 from the vessel 1 (the latter being forked or branched)enter the vessel 21 below the partitions 24. In the bottoms of thechambers of the vessel 21 are evacuating or draining outlets 25, and apipe 26, having forked connections with the chambers in vessel 21,carries off the gases (CO) from the same to the burners or heaters 12and 16.

Figs. 3 and 5 show how hot or warm air mixed with carbonic oxid from thevessel 21 is supplied to the burners of sections C and S. The air fromflues 27 in the masonryenters a tube-like jacket 28, through whichextends a jet-tube 29, connected with the gas-supply pipe 26.

It is proposed with this apparatus to separate metals, and especiallythe metals of the alkaline earths,from the substances combinedchemically with them; and the apparatus may be employed in carrying outother processes-as, for example, the preparation of soda, chlorids, andother similar combinations.

The operation of the apparatus will perhaps be best understood bydescribing how it is used in the separation of the metal aluminium fromalumina, (A dehydrated and mixed according to their equivalents withpitch or resin, so as to form balls of from fifteen to eighteencentimeters in diameterin the proportion Al O +3C. In the vessel 1 ofthe section E is poured an electrolyte consisting of sodiumch1orid,(NaOl,) whichis kept in a liquid state by the heater below at atemperature of from 900 to 1,000 centigrade. To the electrolyte will beadded in small proportions the chlorids of potassium, lithium,strontium, or calcium in such a manner as to increase the fluidity andrender negligible the portion of the electrolyte evaporated. Thesechlorids remain always in the bath, their action herebeingsimplycatalytic. The electrolysis is produced as follows: Ghlorinis developed at the anodes 4, passes up to the space between the covers3 and 5, and from there passes off by the pipes 13 to the bottom of thevessel 15 of section 0. The auxiliary vessel 9, as stated before, is thereceiver for the electrolyte, and the apertures 7 will always be belowthe level of the liquid. The flattened separating-tubes 2 are made todip into the electrolyte, so as to seal their lower ends, say, tenmillimeters; but they do not extend to the bottom of the vessel 1. Thedisposition of these separators 2 is such thatas soon as the chlorin andsodium are liberated from the salt and pass to the respective anodes andcathodes they become separated permanently by the tubes 2. The sodiumpasses off by the pipe 14: to the vesse121 ofthe section S. The vessel15 of the section 0 is charged with the balls of alumina and tar, whichrest on the perforated bottom 18. The chlorin gas entering by the pipes13 passes up through the mass on the perforated platform or bottom tothe space above the mass. By reason of its affinity for aluminium thechlorin decomposes the alumina, forming aluminium chlorid, While theoxygen set free from the alumina combines With the carbon of the tar orrosin to form carbonic oxid, (C0,) the reaction being The aluminiumchlorid mixed with carbonic oxid flows by the pipes 20 to the vessel 21of the section S. These pipes, as well as those before mentioned, shouldbe well protected against radiation of heat in order to maintain thesubstances passing through them in a state of vapor. The vapor ofaluminium chlorid mixed with the carbonic-oxid gas on entering thevessel 21 mixes thoroughly with the hot sodium vapor from the vessel 1and a double reaction takes place. The chlorid is decomposed and thecarbonic oxid separated, as expressed in the following formula:

The sodium chlorid thus obtained and the aluminium will be found mixed.

To separate the aluminium from the sodium chlorid with the aid of thisapparatus, so as to produce the metal in the form of bars or bricks, themixture of the metal and the chlorid is put in the auxiliary vessel 9 ofthe section E. The sodiu m chlorid is at once taken up by theelectrolyte and the heavier aluminium in a molten statefalls to thebottom and may be drawn ofi at the pipe 11, as before explained. Fig. 3shows a ladle 30 to receive the molten metal and convey it to the molds.The purpose of dividing the vessels and 21 of the respective sections 0and S into two parts or chambers, as shown, is to enable one chamber tobe emptied and cleaned while the other is in operation, thus avoidinginterruption of the process. Suitable stop-cocks 31 are provided in theseveral pipes to enable this to be effected.

Only one section E or electrolytic section is herein shown; but it willbe obvious to any one skilled in the art that several of theseelectrolyzers may be employed in connection Witha single largechlorinating apparatus O and a single large substitution apparatus S. V

It may be stated as to the electrolyzing apparatus that spaces occupiedby the electrolyte between the anodes and cathodes may be about one andone-half centimeters, and the superficial area of the anodes may equalthat of the cathodes. There may be for each dynamic horse-power onehundred square centimeters of area of the electrodes. In thesemeasurements the entire exposed faces of the electrodes are counted.These superficial areas extend to one hundred and fifty squarecentimeters for kilowatt; but this can be reduced about one-fourth. Agood proportion for the capacity of theelectrolytic bath or containingvessel Will be about one-half liter per horse-power or three-fourthsliter per kilowatt. The thickness of the carbon anode may be 1.9centimeters and that of the iron cathode 0.1 centimeter. The form of theseveral receptacles or vessels will vary with the dimensions and outputof the plant.

This process is applicable to the separation of any'metal from itscompound where its chlorid is less exothemic than sodium.

The anhydrous chlorid is first formed, even though the mineral treatedmay be sulfurous, and sodium is then substituted for the base of thechlorid, thus setting the metal free.

I do not herein claim the apparatus shown and described, as thisinvention is limited to the process; but I have described and claimedthis apparatus in another application, Serial No. 85,772, filed December13, 1901.

Having thus described my invention, I claim 1. The herein-describedmethod of obtaining a metal from its compound, which consists inseparating sodium from its chlorid, while at a high temperature, byelectrolysis, then decomposing the oxid of the metal treated while hot,with the chlorin from the first step,whereby a chlorid of the metal isformed,

ments, then passing the hot chlorin from the first step through aluminamixed with a carbonaceous substance, thereby producing, by reaction,carbonic oxid and aluminium chlorid, and then mixing with the hot,vaporous aluminium chlorid the hot, vaporous sodium from the first step,thereby producing, by reaction, sodium chlorid and aluminium in metallicform, substantially as set forth.

In witness whereof I have hereunto signed myname, this 26th day of June,1901, in the presence of two subscribing witnesses.

GIROLAMO TADDEI.

Witnesses:

SEooNDo TORLA, VITTORIO GARNIER.

